This application claims the priority benefit of Taiwan application Ser. No. 89123368, filed Nov. 6, 2000.
1. Field of Invention
The present invention relates to a scanning system. More particularly, the present invention relates to a scanning system that scans a three-dimensional object.
2. Description of Related Art
The photoelectron detector in a conventional three-dimensional coordinate scanning system uses a grab device, such as a camera. The grab device is built with an axis-symmetrical lens and an image sensor, such as a CCD. The ratio of the measuring depth and width of the photoelectron detector depend on an angle between the projecting optical trace of the photoelectron detector and the image-capture optical trace of the camera, where both traces intersect at a region of the object. According to the triangulation principle, the angle between the projecting optical trace and the image-capture optical trace is smaller and the shielding effect is lower. The detector size is also smaller, but the difference between the measuring depth and width is greater. For example, when scanning a human face, the measuring width is 200 mm and the measuring depth is 1200 mm. However, the measuring depth of a conventional three-dimensional scanning system is only up to approximately 300 mm, which is only a quarter of the measuring depth range for the human face. Therefore the resolution of the depth is worse.
Because the photoelectron detector measures an optical line one at a time, a scanner needs to be arranged to allow the photoelectron detector to move relative to the object, therefore every region of the object can be measured by the scanner. This method uses mechanical positioning abilities to measure the different regions of the object and register the data. All the data is registered using an identical coordinate system. A conventional scanner generally has a multi-movable axle and a revolving spindle (e.g., an XYZ three-movable axle and a revolving spindle). When the number of axes is greater, the amount of dead space measured can be decreased. However, this kind of scanning system has many disadvantages. For example, the scanning system is large and bulky and cannot be moved easily. The measurement range is limited by the limitations of the scanning system""s range of movement. Also, the manufacturing cost is very high.
The above system uses multi-view data registration, which uses the mechanical positioning method to record and return the data of different measured positions to an identical coordinate system. These days, software technology for positioning is emerging and developing continuously, and accordingly, there are now many methods for positioning. For example, there are methods that use the geometric features of the object, the surface color of the object, or the reflectivity of the object. Therefore, using the mechanical positioning method to register data is no longer necessary.
In the software positioning method, a common region is obtained from the data measured at many different locations on the object. The relationships between the locations and the coordinate system are worked out, and the relationships refer back to the same coordinate system. Therefore, the scanner uses the plane-scanning method that is, one area region of the object is scanned in each scan. The conventional method measures a fixed angle from a light source hitting the scanning mirror, and the camera is fixed in a set position. Because the optic axis and the camera""s optic axis are constantly changing, the camera lens cannot focus all the light planes of the different angles. If the lens focuses one light plane of one angle, the image quality of the other light planes of the other angles will be worse. If the angle deviates from the focus plane, the image quality will be worse (the light stripe will become hazy and rough). The quality of the measurement will be affected, and the precision of the measurement will be reduced.
Moreover, aside from grabbing the image from the light stripe, the camera also grabs an image from the background environment. In order to grab a light stripe, the commercially sold frame grabber needs to use a software method that performs complex image processing steps. This method requires a lot of time, which in turn affects the scanning speed.
The invention provides a three-dimensional scanning system.
As embodied and broadly described herein, the invention uses the anamorphic principle and provides a different rate of image magnification between the horizontal and vertical directions. The resolution can be adjusted between the measuring depth and the measuring width, and also can be applied in different measuring situations to increase the resolution.
The invention provides a three-dimensional scanning system and it uses the software registration method without the multi-axle scanner. The measuring range is not limited, and the photoelectron detector can be moved randomly.
The invention provides a three-dimensional scanning system. The scanning system can solve the problem of an unfocused image, where the angle is fixed between the project-track and the camera optical track. Therefore when the light plane scans in a different region, the light stripe can focus on the image plane and obtain the best measurement quality.
The invention provides a three-dimensional scanning system that can provide an image processing circuit and can completely grab a light stripe without grabbing the environmental light around the object.
The three-dimensional scanning system of the present invention can scan and calculate the three-dimensional coordinate data from an object""s surface. The three-dimensional scanning system comprises a photoelectron detector, a rotational scanning device, a drive device, an image-capture circuit and an operational control device. The photoelectron detector creates a light plane to scan on the object, and receives the reflected light stripe from the object""s surface. The rotational scanning device couples with the photoelectron detector that is placed in a fixed axis and is rotated, and the light stripe is allowed to scan the object. The drive device couples to and operates the photoelectron detector and the rotational scanning device. The image processing circuit can grab the light stripe instantly. The operational control device couples with the rotational scanning device and the photoelectron detector. It controls the motion of the rotational scanning device and the scanning position of the photoelectron detector and calculates the three-dimensional coordinates of the object.
In the foregoing, the photoelectron detector includes a projecting device and an image-capture device. More particularly, the projecting device projects the light plane along the optical trace and forms the light stripe on the object""s surface. The image-capture device has a fixed angle between an image-capture optical trace and the projecting optical trace, and receives the reflected light stripe from the object surface.
In the foregoing structure, this invention of the three-dimensional scanning system has a simple machine structure. The simple rotational scanning device and the photoelectron detector without the multi-axles can have a small body size, the manufacturing cost is lower, and the device can be portable. The photoelectron detector includes an anamorphic optics device and a light source. The anamorphic optics device can adjust the magnifying power of the horizontal and vertical directions, and also can adjust the measuring depth and the measuring width, and increase the resolution. The light source can be a laser, for example. It scans according to a fixed angle between the projecting optical trace and the camera optical trace in a range and allows the light stripe that comes out to have the best image quality.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.